The improved linkage is adapted to be employed for the support of, and for the opening and closing of, casement type or transom type windows permitting pivotal movement of the window sash about a vertical or horizontal axis. The linkage is adapted to be connected between a conventional window frame and a window sash, whether the structures be formed of metal or wood. This type of window frame and sash configuration is illustrated in the Anderberg U.S. Pat. No. 2,784,459 issued Mar. 12, 1957, which is referred to and incorporated herein by reference. Typically, these types of windows include a stationary window frame which is attached to and built into the walls of a building, and a window sash adapted for mating within said frame. Both the sash and frame typically are similar in cross-section and formed from extrusions in the form of "Z" bars having webs with extended inner and outer lips so that when the window sash is fitted within the window frame, the outer lip of the window sash bears against the entire perimeter of the corresponding window frame and the inner lip of the window frame is engaged by the lip of the window sash. The pair window support linkages are mounted in an accommodation space between the sash and the frame with one at the top and one at the bottom in case of a vertically hung window, or one on either side in case of a horizontally hung window. Other patents disclosing windows and supporting brackets of this type are the Anderberg and Taylor U.S. Pat. Nos. 3,345,777 issued Oct. 10, 1967, 4,042,266 issued Aug. 16, 1977, and 3,722,142 issued Mar. 27, 1973, all of which are referred to and incorporated herein by reference. However, while these patents disclose devices which are effective in allowing for the opening and closing of a window sash upon a window frame, they do not provide the advantages of the present invention such as allowing for the maximum open space possible for a given frame dimension for the escape of an individual therethrough in case of a fire. The prior art windows swing to an open position substantially spaced from the edge of the opening which with some arrangement, positions the window near the middle of the window opening thereby blocking escape by a person unless the window is very large.
This problem has been emphasized recently by various building and safety regulations and state laws that require buildings to have escape windows with a sufficient opening it its open position to allow the escape of a human being. Some codes require one such escape window in each bedroom on the first and second floors. Generally, an escape window must provide an opening of at least 21" and it must latch open. Because of the requirements mandated by these regulations, conventional devices, including those described in the prior art have been unsatisfactory.